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Saturday, June 27, 2020

What is Arrhenius equation ?

The temperature dependence of rate of a chemical reaction can be accurately explained by Arrhenius equation. It was first proposed by Dutch chemist   J.H. Vant’s Hoff but Swedish chemist Arrhenius provides its physical justification and interpretation.


 K= Rate constant

 A= Arrhenius constant or frequency factor or pre exponential factor

 R= Universal gas constant =25/3 joule per mole per second

Ea= Activation Energy

 T= temperature

-Ea/RT= Boltzmann factor or fraction of molecule having equal or greater than Activation energy or fraction of molecule that have kinetic energy greater than activation energy.

Related Questions:

(1) What is Arrhenius equation ?

(2) what happen when activation energy of a chemical reaction becomes equal to RT?

(3) What is the activation energy and how to different from threshold energy ?

(4) In Arrhenius equation for a certain reaction, the value of A and Ea (activation energy) are 4 × 10^13 sec–1 and 98.6 kJ mol–1 respectively. At what temperature, the reaction will have specific rate constant 1.1 × 10^–3 sec–1?

(5) The energy of activation for a reaction is 100 kJ mol–1. Presence of a catalyst lowers the energy of activation by 75%.What will be effect on rate of reaction at 20ºC, other things being equal?

(6) A drug becomes ineffective after 30 % decomposition. The original concentration of a sample was 5mg/mL which becomes 4.2 mg/mL during 20 months. Assuming the decomposition of first order , calculate the expiry time of the drug in months. What is the half life of the product?

(7) A first order reaction is 20 % completed in 10 minutes. Calculate the time taken for the reaction to go to 80 % completion. 

(8) The rate of a reaction triple when temperature changes from 20”C to 50”C. Calculate energy of activation for the reaction (R = 8.314 JK^1 mol^1).

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